Armed police raided the home of two respected foster carers in their hunt for the bomb factory used by the Parsons Green bomber today, just hours after arresting an 18-year-old man close to the port of Dover.

The rapidly moving developments came a day after commuters fled in terror after a homemade bomb partially detonated on a District Line train, injuring 29 people.

Kent police detained the teenager close to the Port of Dover at 7.50am on suspicion of being a terrorist, describing it as a “significant arrest”.

Police officers were later seen searching bins close to Dover Priory rail station a few minutes walk from the port.

The suspect is due to be moved to a south London police station tonight.

Deputy Assistant Commissioner Neil Basu, of the Metropolitan Police, said: "We have made a significant arrest in our investigation this morning. Although we are pleased with the progress made, this investigation continues and the threat level remains at critical.

"The public should remain vigilant. This arrest will lead to more activity from our officers."

The arrest place to close to the busiest ferry hub in Europe, which serves as a commercial gateway to the French coast, including Calais and Dunkirk - raising the prospect the suspect could have been attempting to leave the country.

Five hours later armed police backed by the bomb squad arrived at an address in Sunbury-on-Thames, south west London, and began evacuating residents from surrounding homes.

The elderly owners of the Cavendish Road property, Penelope and Ronald Jones, are a dedicated foster couple who have taken in hundreds of young people since 1970, including refugees from several countries.

In 2009 Mr and Mrs Jones were appointed MBEs for services to children and families. The honour was presented to them by the Queen at a ceremony at Buckingham Palace.

Mrs Jones, 71, and her husband, 88, said at the time: “We open our hearts to all the children. Anybody that comes to us we will do whatever we can to help them with whatever they need.”

Their home is 11 miles from Parsons Green and on the overground rail line to Wimbledon, which is on the District Line. The couple were unavailable for comment.

A neighbour who gave her name as Daphne, who lives opposite the house that was raided on Cavendish Road, said: ''I am so worried about Ron and Penny, they are a lovely couple.”

The improvised explosive device in a white bucket blew up on the final carriage of the Parsons Green trainCredit:
Pricey1983aa/Twitter

Mojgan Jamali, who lives close to the house, said: "I was in my house with my children and there was a knock at the door from the police.

"They told me to leave. They said: 'You have one minute to get out of the house and get away.'

"I just got out, I got my three children and we left the house and the street.”

Friday's device reportedly contained the explosive triacetone triperoxide (TATP) and nails, but is thought to have only partially detonated from inside a bucket.

There were fears the number of those hurt could have been much higher had the bomb, which was concealed within a supermarket carrier bag, fully exploded.

It is not yet known whether the device, which was reportedly fixed with a timer, went off at its intended target or whether it was intended to go off further into central London.

The train, which was bound for Edgware Road, was just pulling into the station in south-west London when the device detonated in the rear carriage, sending passengers fleeing to safety.

Amber Rudd, the Home Secretary, speaking after a meeting of the Government’s Cobra emergency committee, said: "There is no doubt that this was a serious IED, it was good fortune that it did so little damage in fact."

Assistant Commissioner Mark Rowley said police were "chasing down suspects", indicating that a potential network of plotters could have been involved in the Parsons Green attack.

The Met said it has spoken to 45 witnesses and 77 images and videos have been sent to detectives by members of the public.

A key plank of the investigation has focused on CCTV, with officers combing through footage to establish who planted the device, and when and where it was placed on the train.

Security minister Ben Wallace suggested CCTV images of the bomber could be released as part of the manhunt, but Scotland Yard subsequently denied there were any plans to do so.

Troops have been dispatched to key sites across the country to free up armed police officers after the country's terror threat level was raised to its highest point.

The threat level remains at critical, which means a further attack is feared to be imminent.

In a move to reassure Londoners, the Met Commissioner Cressida Dick joined uniformed officers on patrol, travelling by tube to Waterloo Station and walking along the South Bank.

The army will deploy troops at key locations around the capital in order to free up police who were last night involved in a huge manhunt to catch the terrorist responsible for the failed Parsons Green bomb attack, which Islamic State of Iraq and the Levant claimed responsibility.

Witnesses described scenes of terror and panic after the blast sent a "fireball" and a "wall of flame" through a District line service in west London.

But the main device, which had been fitted with a crude timer using shop-bought fairy lights, failed to detonate, meaning hundreds of people were spared death and serious injury.

Anti-terror police are understood to be working on the theory that the bomb was detonated early by accident and that the intended target may have been the Tube station at Westminster.

A police officer at the entrance to Parsons Green after the station re-opened overnightCredit:
Jonathan Brady/PA Wire

The attack - the fifth terrorist attack on the UK in just six months - caused a diplomatic row between Washington and London.

Donald Trump seemed to accuse the Metropolitan Police of knowing the identity of the attacker in advance but failing to prevent the bombing. Mr Trump posted on Twitter: “Another attack in London by a loser terrorist. These are sick and demented people who were in the sights of Scotland Yard. Must be proactive!”

His claim earned the US President a stiff rebuke from Theresa May. “I never think it’s helpful for anybody to speculate on what is an ongoing investigation,” said the prime minister. “The police and security services are working to discover the full circumstances of this cowardly attack and to identify all those responsible.”

Despite Mr Trump’s suggestion that the terrorist was known to police, counter-terrorism sources insisted that was not the case and that the hunt for the perpetrator of the bombing on a District Line train was ongoing.

An injured woman is assisted by a police officer close to Parsons Green stationCredit:
Stefan Rousseau/PA

Counter terrorism specialists from Scotland Yard were working to establish his identity from CCTV footage on the train and at stations on the line. They were also combing through records of payments with Oyster cards used to buy Tube tickets.

One theory is the suspected bomber may have fled the scene among the stampede of panicking passengers and escaped among the crowds.

They were also uncertain that Parsons Green was not the planned target, pointing to reports that the bomb, which was packed with shrapnel and contained a timing device, had apparently malfunctioned.

Witnesses reported seeing people "covered in blood" after a "flash and a bang" from the device, but sent a "fireball" through the packed Tube train.

Pictures and video posted on social media showed a flaming bucket - which appeared to have wires coming from it - inside a Lidl carrier bag on the floor of a carriage.

The device is not believed to have fully detonated and it is reported that it could have been set off on a timer.

Residents evacuated at Sunbury address

The Met Police said police officers had evacuated and were searching a residential address in Sunbury-on-Thames.

Scotland Yard said: "The evacuation is a precautionary measure following the arrest of a man in Dover, Kent, at approximately 07:50hrs this morning in connection with the investigation into the terrorist attack at Parsons Green Underground Station on Friday, 16 September.

Officers began evacuating the address at approximately 13:40hrs today.

Residents in the buildings immediately surrounding the address are also being evacuated as a precautionary measure.

Cordons are being put in place at a 100 metre radius to facilitate the Metropolitan Police Service’s operation, which is being supported by colleagues from Surrey Police.

A search of the address is ongoing and the cordons will remain in place until the operation is complete.

Police would like to thank the local residents directly affected for their cooperation and patience. Local officers are on duty in the immediate area to talk to the community and address any concerns that they may have.

Met Police Commissioner Cressida Dick says London "will not stop"

London will not be stopped by terror, Metropolitan Police Commissioner Cressida Dick has said as she highlighted an increased visible police presence on the capital's streets.

Ms Dick spoke as she joined officers on some of the city's busiest streets, travelling on the Tube to Waterloo Station and patrolling the tourist hot spot of the South Bank

She said: "London has not stopped after other terrible attacks and it will not stop after this one."

The Commissioner said the public should feel "utterly reassured" by the presence of police.

She said: "I've been out and about today. The public seem to be very positive about the number of officers that we have."

She added: "The great thing about London is that we don't give in, we don't give in to terrorists - we never have and we carry on.

"So the transport system is running just as it ever did and the events are going ahead today. People are out and about. I've spoken to lots of people, Londoners and tourists and business people. People are here and I would say, carry on about your business and secondly, of course, be vigilant."

She added: "My main message is London is carrying on. Carry on with your business but be alert, don't be alarmed but make sure you tell us anything that worries you."

Scotland Yard describe the arrest as "significant"

The 18-year-old was arrested by Kent Police in the port area of Dover under section 41 of the Terrorism Act.

Deputy Assistant Commissioner Neil Basu, Senior National Co-ordinator for Counter Terrorism Policing, said: “We have made a significant arrest in our investigation this morning. Although we are pleased with the progress made, this investigation continues and the threat level remains at critical.

“The public should remain vigilant as our staff, officers and partners continue to work through this complex investigation. We are not, at this time, changing our protective security measures and the steps taken to free up extra armed officers remain in place.

“This arrest will lead to more activity from our officers. For strong investigative reasons we will not give any more details on the man we arrested at this stage.”

Man, 18, arrested in Dover

Tightened security ahead of Chelsea v Arsenal game

In a statement, Chelsea said: "Following Friday morning’s incident at Parsons Green, and in order to help us fully prepare for the game, the majority of the Stamford Bridge site will remain closed until Sunday morning.

"This includes Stadium Tours, the Museum, Megastore and the Chelsea Health Club & Spa, while the ticket office will be operating via telephone and online only.

"During that time, entrance to the site will be via the Stamford Gate entrance only. On Sunday, we urge supporters to arrive at least one hour before kick-off to allow for extra security measures.

"We also request that supporters do not bring bags as this will delay your entry to the stadium. The club continues to monitor events and liaise with the police and relevant authorities on supporter safety."

Trump under fire in US over London bombing comments

Ben Cardin, a Democratic member of the Senate Intelligence Committee, backed Theresa May in her rebuke of Donald Trump over the London bombing David Millward reports.

“I think the Prime Minister of the UK was appropriate in calling the president out.”

John Cohen, former US counterterrorism official and now a professor at Rutgers University, also believed Mr Trump’s intervention was unhelpful.

“At this stage investigators are going to be doing everything they can to locate those involved in the attack, and in particular the bomb maker,” he told the New York Times.

“These types of statements — at this stage of the investigation — can undermine law enforcement efforts because it discloses key information that the investigators may be using to locate the attackers, and it could put peoples’ lives at risk.”

Bomb 'highly likely' to be TATP - CNN

A source briefed by investigators told CNN that an initial assessment of the device indicates it is "highly likely" to have contained the explosive TATP but that this has not been confirmed. It also appeared to have been crude and poorly designed, the source said.

President Trump speaks to PM to express sympathy

The White House press secretary has revealed details of the phone call between Donald Trump and Theresa May. The US president phoned to "convey his sympathies and prayers for those injured in the terrorist attack today in London", the White House said.

"The President pledged to continue close collaboration with the United Kingdom to stop attacks worldwide targeting innocent civilians and to combat extremism. "

A Downing Street spokesman said: "President Trump called the Prime Minister earlier today to offer his condolences over this morning's cowardly attack in London.

"They also discussed North Korea's latest missile test, agreeing it was a reckless provocation and that China must now use all its leverage to bring pressure to bear on the North Korean regime to ensure they change course and end these illegal tests."